projects: file explorer, ws improvements, i18n, and fs routing

Add project-files component with tree navigation. Extend UserFs with
shared-folder resolution. Wire API routes for file browsing. Improve
WS session lifecycle and project-board layout. Add i18n keys for
projects and inbox across all locales.

web/i18n/en.js

@@ -221,7 +221,26 @@ export default {
   'projects.share.access.write':    'Write',
   'projects.share.access.readonly': 'Read-only',
   'projects.share.access.readwrite':'Read & write',
-  'projects.files.placeholder':     'The project files live here. Open the chat to work in this folder — a file explorer is coming.',
+  'projects.tabs.files':              'Files',
+  'projects.tabs.sharing':            'Sharing',
+  'projects.files.col.name':          'Name',
+  'projects.files.col.created':       'Created',
+  'projects.files.col.modified':      'Modified',
+  'projects.files.col.size':          'Size',
+  'projects.files.empty':             'This folder is empty.',
+  'projects.files.refresh':           'Refresh',
+  'projects.files.drop':              'Drop files here to upload',
+  'projects.files.btn.new_folder':    'New folder',
+  'projects.files.btn.upload':        'Upload',
+  'projects.files.uploading':         'Uploading…',
+  'projects.files.action.rename':     'Rename',
+  'projects.files.action.delete':     'Delete',
+  'projects.files.confirm.delete_file': 'Delete "{name}"?',
+  'projects.files.confirm.delete_dir':  'Delete the folder "{name}" and everything inside it?',
+  'projects.files.modal.mkdir':       'New folder',
+  'projects.files.modal.rename':      'Rename "{name}"',
+  'projects.files.modal.name':        'Name',
+  'projects.files.error.name':        'Enter a valid name (no slashes).',
 
   // ── Project detail ──────────────────────────────────────────────────────────
   'project_board.back':               'Projects',